On Saturday, August 12, 2000, Russia's nuclear submarine Kursk fell to the bottom of the Barents Sea while on a training mission in international waters near the Arctic Circle.
The 14,000-ton submarine settled 354 to 450 feet down, trapping 118 sailors.
Possible causes of the accident were a collision (favored Russian explanation, perhaps as the Kursk rose to periscope level), an onboard explosion (most likely explanation, probably involving a torpedo and triggering further detonations), or hitting a WWII mine.
Nuclear reactors powering the ship were taken off line and no radiation leaks detected.
The only contact with crew, SOS signals tapped on the hull, stopped Tuesday.
Probes revealed massive damage to the front of the vessel and a large hole in the hull.
Repeated efforts to hook up air and fuel lines and dock with the escape hatch were frustrated by bad sea conditions.
The Russian navy had no advanced rescue vessels so several countries, including the US, offered help.
Russia rejected a French offer.
On Tuesday it approached NATO about help and by Wednesday accepted British and Norwegian offers.
Rescue vehicles arrived Saturday.
Rescue operations ended two days later when divers opened the hatch and found the sub filled with water.
There were no survivors.
Putin's government was criticized for its delay in accepting help.
Lifting the Kursk to the surface would take a year and be costly and might never be done.
Sailors' bodies were to be retrieved in October or November by cutting holes in the hull.
